Packages suitable for heating in a microwave are known, for example, from EP 661 219 A, WO 03/051745 A, WO 04/13015 A or EP 1 714 908 A.
In this case, the packages have valves of different type and shape.
The reclosability of the packages is usually provided by adhesive coatings in an edge zone of the package. However, even when the sealable coating is slightly contaminated, the package is no longer completely closable.
Further known from EP 1 721 833 A1 is a self-venting, reclosable bag in which one or more discontinuities are provided in a seal layer between the inner surface of the plastic film of the bag and a portion of the zipper. These discontinuities are described as a gap and allow hot air or steam to escape through them from the interior of the bag.
A bag having a device for the escape of steam is likewise further known from JP 2000-72156, wherein this bag has permanent openings between the inner surface of the plastic film of the bag and a portion of the zipper in the transverse direction to the zipper. These permanent openings are disclosed as channels having constant cross-section or constant width.
US 2004/0069157 A1 also discloses a device for the escape of steam in connection with a bag, wherein this device is disclosed in the present case by pseudo-closed gaps in a polymer layer of the film.
The solutions disclosed in connection with a zipper frequently prove to be problematical because the channels or gaps between the inner surface of the plastic film and a portion of the zipper are frequently laid through moisture and the so-called glass plate effect significantly impairs a reliable opening of these gaps or channels. The sufficiently known glass plate effect substantially involves two glass plates between which moisture enters being barely able to be separated from one another, or only with expenditure of extreme force. This effect is particularly important in the steam cooking of food in a bag, which is for example reclosable by means of a zipper because the regions of channels or gaps possibly “adhering to one another” due to moisture can no longer ensure a controlled escape of steam and possibly an undesired opening of the zipper can occur so that the steam-cooking effect of the bag is lost.
It was the object of the invention to provide a reliably reclosable bag which is in particular suitable for the steam cooking of packaged food and has a valve for the escape of steam during the cooking process.